(1) Field of the Invention
The present invention relates to a method of arranging a buoyancy system on an aircraft, to a buoyancy system for an aircraft, and to an aircraft provided with a buoyancy system.
The invention thus lies in the technical field of buoyancy systems enabling an aircraft, and more particularly an aircraft having a rotary wing, to ditch on water and to float in stable manner thereon.
Such a buoyancy system contributes to providing an aircraft with buoyancy and stability on ditching. When ditching has been forced, the buoyancy system may be used in particular in order to enable the occupants of the aircraft to be evacuated therefrom.
(2) Description of Related Art
A buoyancy system may comprise inflatable floats that are deployed either on command of the pilot and/or the copilot, or else on being triggered automatically, in particular by one or more immersion detectors. Such floats may comprise bags that are inflated by explosive or electrical deployment means, for example.
Under such circumstances, an aircraft may have a float that is arranged in a compartment. The compartment is then open to the outside in order to allow the float to be deployed. The aircraft may also have closure means for closing the compartment other than while ditching, while nevertheless enabling the compartment to be opened prior to ditching in order to deploy the float.
Conventionally, a float may comprise an inflatable bag folded in the volume available inside a compartment.
In a first embodiment, the float is fastened to a compartment of an aircraft, e.g. by straps. The compartment is also closed by a flexible tarpaulin.
Thus, when the float inflation means are activated, the volume of the float increases. Since the tarpaulin is flexible, it gives way under the pressure exerted by the float. The float then deploys so as to become operational.
In a second embodiment that is better optimized in terms of aerodynamics and/or appearance, the float is arranged in a compartment that is closed by a cover that is semirigid or rigid. A cover that is semirigid or rigid is referred to below as a “rigid” cover. A rigid cover is thus a cover that retains its shape under normal conditions of use, unlike a flexible cover and/or a flexible tarpaulin.
In a first variant of the second embodiment, an inflatable float is fastened to the aircraft, e.g. by straps, the compartment being closed by an ejectable cover. The cover can thus be ejected in order to enable an inflatable float to be deployed. Nevertheless, that variant can lead to harmful ejection of a cover towards an element of the aircraft, or indeed towards an inhabited region. Such ejection might be caused by untimely opening.
When overflying a stretch of water, the cover may also be ejected onto the liquid surface being overflown. Under such circumstances, when ditching, the ejected cover can become jammed between said liquid surface and the aircraft. The cover then runs the risk of giving rise to damage.
In a second variant of the second embodiment, an inflatable float is fastened to the aircraft by straps, with the compartment being closed by a cover that is rigid and movable, being hinged to the fuselage. The cover may optionally be a door that is fastened to the fuselage by a plurality of hinges.
The cover can thus be moved so as to allow an inflatable float to be deployed. For example, the cover may pivot in order to open the compartment.
That variant is advantageous, but implementing it can be complex.
Furthermore, the cover may constitute a danger at the time of ditching, depending on its location. Such a rigid and movable cover will be moved under the impact of ditching. The cover can therefore become wedged against the aircraft and/or the float, and runs the risk of damaging a portion of the aircraft and/or of the float.
In a third variant of the second embodiment, the cover is fastened to the inflatable float. The inflatable float is thus folded and then attached to the cover, e.g. by adhesive. The assembly comprising the float and the cover is then inserted into the compartment.
That third variant is advantageous. While the float is being deployed, the cover is moved away from the aircraft. Any risk of the cover damaging the aircraft is therefore reduced.
Nevertheless, folding the float can be difficult.
In addition, that configuration makes access to the compartment more complex. Since the inflatable float is contained in the cover, opening the cover, e.g. for maintenance purposes, can be dangerous.
In this context, it can be seen from the state of the art that installing an inflatable float on an aircraft is far from straightforward and raises numerous difficulties.
The state of the art includes document U.S. Pat. No. 3,004,737. That document describes a cover that is hinged to a fuselage.
Document FR 1 599 828 relates to landing gear for an aircraft. An inflatable tube is retracted into an enclosure formed by flexible covering elements.
Document U.S. Pat. No. 8,079,547 describes an emergency float combined with an emergency raft.
Document U.S. Pat. No. 4,655,415 discloses an emergency float attached to the landing skid of an aircraft.
Document U.S. Pat. No. 7,156,033 describes an airplane having a buoyancy system including an ejectable cover.
Document FR 2 517 620 describes a float having a protective shield.
Document EP 0 001 607 describes landing gear provided with a float.